I remember the day my father told me about the sociological phenomenon whereby trends that begin at the very top of our society gradually filter down until, eventually, they reach the very bottom.

I was sceptical.

"D'you mean to tell me that something as idiotic as that," I said, pointing to a pretty young debutante with a pair of sunglasses on her head, "will eventually be adopted by every young woman in the country? I don't think so."

Now I know better, of course.

Another case in point is the continuing success of Quaglino's, the 300-seater gastrodome on Bury Street which recently hit the headlines when five of its staff were arrested by immigration officers. A famous "society" restaurant in the 1930s, Quaglino's was re-launched by Sir Terence Conran in 1993 and, for a few months, enjoyed the distinction of being the most fashionable restaurant in London. I remember Julie Burchill hosting a 30th birthday party for me shortly after it opened and being astonished that she'd managed to get a table. Thirteen years later, and Quaglino's is about as untrendy as it's possible to be--it's one up from an Angus Steak House--and yet, incredibly, it's still popular. Only this Christmas, for instance, Quaglino's served 350 people in the course of a single lunchtime--a house record.

How is this possible? How can anyone, no matter how ill-informed, still think of Quaglino's as glamorous? The answer, according to the sociologists, is that people impersonate the behaviour of those people in the class immediately above them, not necessarily the movers and shakers at the top of the tree. Consequently, the fact that Quaglino's hasn't been considered fashionable by "society" types for at least 10 years is immaterial. The reason it's currently so popular with the bridge-and-tunnel crowd is because, in the not too distant past, it was popular with a group of people that they think of as cool, even if no one else does.

Quaglino's is particularly well-position to capitalise on this sociological phenomenon since it still looks glamorous. Keith Hobbs's interior has held up pretty well since it was first unveiled in 1993. The centrepiece is a grand ballroom staircase that seems tailor-made to make middle-aged ladies from Birmingham feel like they're on the set of a Cecil B DeMille movie. Hard to believe, when making such an entrance, that no actual movie star has darkened the doors of Quaglino's since the Conservatives last won an election.

On the evening I went there with my wife last week, I was consigned to a nasty table-for-two by the kitchen entrance. I tried to sit with my back to the wall, thereby giving myself a view of the restaurant, but my wife was having none of that. She pointed out Gordon Ramsay recently singled this out as one of the rudest things a man can do when taking a woman to a restaurant. Since Gordon can do no wrong in my eyes--he belongs to the social class I aspire to be a member of--I immediately swapped seats. The upshot was that I had to eat my meal facing the wall.

One of the shortcomings of dining in a restaurant that frequently serves over 1,000 people a day is that the food is never going to be particularly special. We each decided to skip the starter and opt for a main course and a pudding--not a great idea, as it turned out. My white pork with prunes and applesauce was fairly non-descript, while my wife's artichoke and wild mushrooms with Hollandaise came without the Hollandaise. Our pudding--a valrhona chocolate plate for two--was a slight improvement, though nothing to write home about.

I wouldn't go back to Quaglino's in a month of Sundays, but I admire its ability to survive for so long past its sell-by date. The question Conran must now ask is: Can there possibly be a group of people even less fashionable than it's current patrons who can take their place in a couple of year's time? It's hard to imagine, but I wouldn't bet against it.